<template>
  <div>
    <div class="goods">
      <div class="menu-wrapper" ref="menuWrapper">
        <ul ref="menuUl">
          <li class="menu-item" :class="{current: index===currentIndex}" 
          v-for="(good, index) in goods" :key="index" @click="clickMenuItem(index)">
            <span class="text bottom-border-1px">
              <img class="icon" :src="good.icon" v-if="good.icon"/>
              {{good.name}}
            </span>
          </li>
        </ul>
      </div>

      <div class="foods-wrapper" ref="foodsWrapper">
        <ul ref="foodsUl">
          <li class="food-list-hook" v-for="(good, index) in goods" :key="index">
            <h1 class="title">{{good.name}}</h1>
            <ul>
              <li class="food-item bottom-border-1px" v-for="(food, index) in good.foods" :key="index" @click="showFood(food)">
                <div class="icon">
                  <img width="57" height="57" :src="food.icon" />
                </div>
                <div class="content">
                  <h2 class="name">{{food.name}}</h2>
                  <p class="desc">{{food.description}}</p>
                  <div class="extra">
                    <span class="count">月售 {{food.sellCount}} 份</span>
                    <span>好评率 {{food.rating}}%</span>
                  </div>
                  <div class="price">
                    <span class="now">￥{{food.price}}</span>
                    <span class="old" v-if="food.oldPrice">￥{{food.oldPrice}}</span>
                  </div>
                  <div class="cartcontrol-wrapper">
                    <CartControl :food="food"></CartControl>
                  </div>
                </div>
              </li>
            </ul>
          </li>
          <!-- class="food-list food-list-hook" -->
        </ul>
      </div>

      <ShopCart></ShopCart>
    </div>
    <Food :food="food" ref="food"></Food>
  </div>
</template>

<script>
  import {mapState} from 'vuex'
  import BetterScroll from 'better-scroll'  
  import CartControl from '../../../components/CartControl/CartControl'
  import Food from '../../../components/Food/Food'
  import ShopCart from '../../../components/ShopCart/ShopCart'

  export default {
    name: "ShopGoods",
    mounted() {
      this.$store.dispatch('getShopGoods', () => { // 回调函数在数据更新后执行
        this.$nextTick(() => { // 列表数据更新显示后执行
          this._initScroll()
          this._initTops()
        })
      })
    },
    data() {
      return {
        scrollY: 0, // 右侧滑动的 Y 轴坐标（滑动过程中实时变化）
        tops: [], // 所有右侧分类 li 的 top 组成的数组（列表第一次显示后就不再变化）
      
        food: {}, // 需要显示的 food
        // menuScrollY: 0, // 左侧菜单栏滑动的 Y 轴坐标
      }
    },
    methods: {
      // 不是与事件相关的方法，加_
      // 初始化滚动条
      _initScroll() {
        // 列表显示之后创建
        this.menuScroll = new BetterScroll('.menu-wrapper', {
          click: true
        })
        this.foodsScroll = new BetterScroll('.foods-wrapper', {
          probeType: 2,
          click: true
        })
        // 给右侧列表绑定 scroll 监听
        this.foodsScroll.on('scroll', ({x, y}) => {
          // console.log(x, y)
          this.scrollY = Math.abs(y)
        })
        // 给右侧列表绑定 scroll 结束的监听
        this.foodsScroll.on('scrollEnd', ({x, y}) => {
          // console.log('scrollEnd', x, y)
          this.scrollY = Math.abs(y)
        })
        // 给左侧菜单列表绑定 scroll 结束的监听
        this.menuScroll.on('scrollEnd', ({x, y}) => {
          // console.log('scrollEnd', x, y)
          this.menuScrollY = Math.abs(y)
        })
      },
      // 初始化 tops
      _initTops() {
        // 1 初始化 tops
        const tops = []
        let top = 0
        tops.push(top)
        // 2 收集
        const lis = this.$refs.foodsUl.getElementsByClassName('food-list-hook')
        // console.log(lis)
        Array.prototype.slice.call(lis).forEach(li => {
          top += li.clientHeight
          tops.push(top)
        })
        // const lis = this.$refs.foodsUl.children
        // 3 更新数据
        this.tops = tops
        // console.log(tops)

      },

      clickMenuItem(index) {
        // 点击左侧，使右侧列表滑动到对应的位置
        // console.log(index)
        // 得到目标位置的 scrollY
        const scrollY = this.tops[index]
        // 立即更新 scroll（让点击的分类项成为当前分类）
        this.scrollY = scrollY
        // 平滑滚动右侧列表
        this.foodsScroll.scrollTo(0, -scrollY, 300)

      },

      // 显示点击的 food
      showFood(food) {
        // 设置 food
        this.food = food
        // 显示 food 组件（在父组件中，调用子组件对象的方法）
        this.$refs.food.toggleShow()
      }
    },
    computed: {
      // 计算属性执行：初始，以及 相关数据发生了变化
      ...mapState(['goods']),
      currentIndex() { // 计算得到当前分类的下标
        // 得到条件数据
        const {scrollY, tops} = this
        // 根据条件计算产生一个结果
        const index = tops.findIndex((top, index) => {
          // scrollY >= 当前 top && scrollY < 下一个 top
          return scrollY >= top && scrollY < tops[index+1]
        })
        // 返回结果
        return index
      },
    },
    watch: {
      // 监听 currentIndex，有变化时进行相应的滚动
      currentIndex(value) {
        // 每个 li 的高度
        const liHeight = this.$refs.menuUl.getElementsByClassName('menu-item')[0].clientHeight
        // 当前展示的分类
        const index = value
        // 屏幕可以展现的分类个数
        const count = 7
        // 当前滚动的距离
        // const {menuScrollY} = this
        // 总共的分类数
        const goodsLength = this.goods.length
        if (index+1 > count) {
          // 基于此案例（总共需要展示的分类较少）采用的滚动策略
          // 当前分类超出可展示的分类数，滚动到底
          this.menuScroll.scrollTo(0, -(goodsLength-count)*liHeight, 300)
        // } else if (menuScrollY !== 0 && index+count < goodsLength){ 
          // 已经向下滚动，且当前分类太靠上，屏幕里不可见
        } else { // 当前分类未超出可展示的分类数，滚动到顶
          this.menuScroll.scrollTo(0, 0, 300)
        }
      }
    },
    components: {
      CartControl,
      Food,
      ShopCart,
    },
  };
</script>

<style lang="less">
  @import '../../../common/less/mixins.less';
  .goods {
    display: flex;
    position: absolute;
    // top: 195px;
    top: 248px;
    bottom: 46px;
    width: 100%;
    background: #fff;
    overflow: hidden;
    .menu-wrapper {
      flex: 0 0 80px;
      width: 80px;
      background: #f3f5f7;
      .menu-item {
        display: table;
        height: 54px;
        width: 56px;
        padding: 0 12px;
        line-height: 14px;
        .text {
          display: table-cell;
          width: 56px;
          vertical-align: middle;
          .bottom-border-1px(rgba(7, 17, 27, .1));
          font-size: 12px;
          .icon {
            display: inline-block;
            width: 12px;
            height: 12px;
            margin-right: 2px;
            vertical-align: top;
            background-size: 12px 12px;
            background-repeat: no-repeat;
          }
        }
        &.current {
          position: relative;
          z-index: 10;
          margin-top: -1px;
          background: #fff;
          color: @green;
          font-weight: 700;
          .text {
            border: none;
          }
        }
      }
    }
    .foods-wrapper {
      flex: 1;
      .title {
        height: 26px;
        line-height: 26px;
        padding-left: 14px;
        font-size: 12px;
        border-left: 2px solid #d9dde1;
        color: rgba(147, 153, 159, 1);
        background: #f3f5f7;
      }
      .food-item {
        display: flex;
        margin: 18px;
        padding-bottom: 18px;
        .bottom-border-1px(rgba(7, 17, 27, .1));
        &:last-child {
          border: none;
          margin-bottom: 0;
        }
        .icon {
          flex: 0 0 57px;
          margin-right: 10px;
        }
        .content {
          flex: 1;
          .name {
            height: 14px;
            line-height: 14px;
            font-size: 14px;
            margin: 2px 0 8px 0;
            color: rgba(7, 17, 27, 1);
          }
          .desc,
          .extra {
            line-height: 10px;
            font-size: 10px;
            color: rgba(147, 153, 159, 1);
          }
          .desc {
            line-height: 12px;
            margin-bottom: 8px;
          }
          .extra {
            .count {
              margin-right: 12px;
            }
          }
          .price {
            line-height: 24px;
            font-weight: 700;
            .now {
              margin-right: 8px;
              font-size: 14px;
              color: rgba(240, 20, 20, 1);
            }
            .old {
              font-size: 10px;
              text-decoration: line-through;
              color: rgba(147, 153, 159, 1);
            }
          }
          .cartcontrol-wrapper {
            position: absolute;
            right: 0;
            bottom: 12px;
          }
        }

      }
    }
  }



</style>
